Sequentially produced alkyl acrylate polymers blended with poly(vinyl halides)

ABSTRACT

PROCESSING AIDS OF IMPROVED DISPERSIBILITY IN LOW MOLECULAR WEIGHT POLY(VINYL CHLORIDE) COMPOSITIONS COMPRISE A SEQUENTIALLY PRODUCED POLYMER CHARACTERIZED BY 1 TO 30 WEIGHT PERCENT OF (A) A FIRST RELATIVELY SOFT STAGE CHARACTERIZED BY A GLASS TRANSITION TEMPERATURE OF 60*C. OR LESS; AND 99 TO 70 WEIGHT PERCENT OF (B) A FINAL SUBSTANTIALLY THERMOPLASTIC STAGE POLYMERIZED IN THE PRESENCE OF A PRODUCT CONTAINING THE FIRST STAGE, AND IN INITIAMATE CONTACT WITH THE FIRST STAGE AND FURTHER CHARACTERIZED IN THAT IF THE MONOMER OR MONOMERS WERE POLYMERIZED IN THE ABSENCE OF THE PRODUCT OF THE FIRST STAGE, A POLYMER WOULD BE FORMED HAVING A GLASS TRANSITION TEMPERATURE OF 25*C. OR GREATER.

United States Patent O US. Cl. 260-876 R 12 Claims ABSTRACT OF THEDISCLOSURE Processing aids of improved dispersibility in low molecularweight poly(vinyl chloride) compositions comprise a sequentiallyproduced polymer characterized by 1 to 30 weight percent of (A) a firstrelatively soft stage characterized by a glass transition temperature of60 C. or less; and 99 to 70 weight percent of (B) a final substantiallythermoplastic stage polymerized in the presence of a product containingthe first stage, and in intimate contact with the first stage andfurther characterized in that if the monomer or monomers werepolymerized in the absence of the product of the first stage, a polymerwould be formed having a glass transition temperature of 25 C. orgreater.

This application is a continuation-in-part of our pending patentapplication, Grochowski, Whang and Graham, S.N. 865,198, filed Oct. 9,1969, now abandoned.

Poly(vinyl chloride) (PVC) compositions, in the absence of a plasticizeror processing aid, are difilcult to process into homogeneous, usefulobjects. The compositions are difiicult to flux and the resulting meltsare heterogeneous and cheesy having poor hot strength and lowelongation. Plasticizers eliminate many of these processing problems butwith a resultant loss in product physical properties, particularlyrigidity.

A class of polymers, notably acrylic, have been developed which improveprocessing properties with little or no resultant loss in physicalproperties. Thus acrylic copolymer processing aids, such as single stagecopolymers of methyl methacrylate and alkyl acrylates, improve therolling bank and other processing characteristics of 'PVC compositionsduring mill processing and extrusion. The acrylic modifiers generallyprovide the most processing improvement when they have physicalcharacteristics, such as glass temperature, approximately equal to thatof the PVC resin sought to be modified, hence relatively hardermodifiers have been developed for use with the relatively highermolecular weight PVC compositions. However, these harder acrylicpolymers do not disperse well in PVC compositions based on relativelylow molecular weight PVC. The acrylic modifiers containing relativelylarge quantities of the softer alkyl acrylate units are more easilydispersed in these compositions, however these softer acrylic polymershave other deficiencies. Thus they are difiicult to prepare-they arecharacterized by low minimum film forming temperaturesand are difficultto handle during their manufacture, such as during isolation proceduresincluding spray drying. Spray drying is an industrially attractivemethod of isolation in that it is rapid and provides a final product ina finely divided form easily dispersible in PVC. These softer polymerstend to agglomerate thus reducing the dispersibility efliciency. ThusWhile some of the softer acrylic copolymers offer improved processingcharacteristics in some ways, their deficiencies somewhat offset theiradvantages.

Acrylic polymers are also useful as impact modifiers in PVC resins. Theimprovement in impact strength imparted through the inclusion of thesemodifiers is derived from their relatively large quantity of soft,elastomeric al-kyl acrylate polymer portion. Thus, when a hard phase isattached to these elastomeric impact modifiers, it is present in arelatively small proportion to the amount of the elastomer in order tobe able to add as little modifier as possible to obtain the highestimpact strength. Generally, these impact modifiers detract from or onlyslightly improve the processing characteristics of the PVC resin.

The present invention provides means for simultaneously upgrading manyof the processing and physical characteristics of acrylic modifiers,while improving the processing characteristics and physical propertiesof the blends of acrylic modifiers in PVC resins. Furthermore themodifiers of the present invention are characterized 'by an improvedease of manufacture. Thus the molecular weights of the acrylic modifiersare easily controllable and the modifiers may be prepared in emulsion athigher solids content. Further, the acrylic modifiers have a higherminimum film forming temperature and may be isolated from emulsion usingnormal spray drying techniques. The acrylic modifiers of this inventionalso do not agglomerate even at high temperature storage conditions.

As an additional advantage of this invention, the acrylic modifiers maybe blended into PVC resins more easily and provide better dispersibilitythan standard high methacrylate content acrylic modifiers. Duringprocessing on heated mills, the acrylic modifiers of this invention arecharacterized by excellent mill release properties.

As a further advantage of this invention, it has been found thatcompositions comprising the acrylic modifiers of this invention and PVCresins are more easily processed in extrusion equipment; in particularmelt fracture and melt viscosity are reduced and die swell is minimized.Finally, advantages of this invention are obtained in final formedproducts using the compositions of this invention. These final formedproducts exhibit higher clarity and improved light transmission as wellas lower odor than the molding compositions based on standard acrylicprocessing aids.

The term molding or forming compositions as used throughout thespecification is not meant to limit use of these compositions, butrefers to the broad class of forming processes, such as injection,extrusion, calendering, blowing film, and other molding processes.

The processing aids of this invention are characterized by a relativelylow proportion of soft stage, i.e. 1 to 30 Weight percent of a firststage having a glass transition temperature of 60 C. or 25 C. or less.The compositions of this invention comprise about 70 to 99' weightpercent of a poly(vinyl chloride) and about 1 to 30 weight percent of asequentially produced polymer characterized by 1 to 30 weight percent of(A) a first relatively soft stage polymerized from a monomer mixture of1.5 to 100 weight percent of an alkyl acrylate wherein said alkyl grouphas 1 to 18 carbon atoms, correspondingly 0 to 98.5 weight percent of atleast one different copolymerizable monoethylenically unsaturatedmonomer, and 0 to 10 weight percent of a copolymerizable polyfunctionalcrosslinking monomer, the first stage further characterized by a glasstransition temperature of 60 C., preferably 25 C., or less; and 99 to 70weight percent of (B) a final substantially thermoplastic stagepolymerized in the presence of the first stage from a monomer mixture ofat least one polymerizable monoethylenically unsaturated monomer to forma polymer in intimate contact with the first stage, stage (B) furthercharacterized in that if said monomer or monomers were polymerized inthe absence of said first stage, a polymer would be formed having aglass transition temperature of greater than that of the first stage andof 25 C. or greater, and preferably 60 C. or greater. It is a criticalaspect of the present invention that the sequentially produced polymerbe characterized by the presence of no more than 30.weight percent ofthe first, relatively soft stage. As will be shown infra in theexamples, improvement in processing characteristics of PVC compositionsdecreases substantially as the proportion of soft stage is increasedabove this level. Preferably the polymer is characterized at 5 to 25,most preferably 5 to 20, percent by weight of (A), the first stage, andpreferably 95 to 75, most preferably 95 to 80, percent by weight of (B),the final substantially thermoplastic stage.

The first stage is polymerized from a monomer mixture of 1.5 to 100, orpreferably 25 to 95 weight percent of an alkyl acrylate wherein thealkyl group contains 1 to 18 carbon atoms. Preferably the alkyl acrylateis one in which the alkyl group contains 1 to 8 carbon atoms. Examplesof suitable alkyl acrylates include butyl acrylate, ethyl acrylate andZ-ethylhexyl acrylate. Ethyl acrylate and butyl acrylate are preferred.The monomer mixture which is polymerized to form the first stage mayalso contain to 98.5 weight percent, or preferably be tween to 75 weightpercent of at least one different copolymerizable monoethylenicallyunsaturated monomer; that is at least one monomer that is not an alkylacrylate, is monoethylenically unsaturated and is copolymerizable withthe alkyl acrylate and any other monoethylenically unsaturated monomerused in forming the first stage.

The term monoethylenically unsaturated monomer comprises a well-knownand precisely defined class of monomers as evidenced by use of this orclosely related terms in the following patents: Balmer et al., U.S.3,224,- 996; Van Hook, U.S. 3,284,399; Cenci et al., U.S. 3,284,- 545;Himei, U.S. 3,288,886; Hall et al., U.S. 3,424,823; Cenci et al., U.S.3,485,775; Hurwitz et al., U.S. 3,536,- 788; and British 963,295.Suitable for use as the monoethylenically unsaturated monomer are alkylacrylates in which the alkyl group contains no more than eighteen carbonatoms, preferably no more than eight carbon atoms; alkyl methacrylatesin which the alkyl portion contains no more than eighteen carbon atoms,preferably no more than eight carbon atoms; acrylonitrile;methacrylonitrile; acrylic acid; methacrylic acid; styrene; andsubstituted styrenes particularly alkyl substituted styrenes wherein thealkyl group contains no more than fourteen carbon atoms. Typical of thesuitable monomers are ethyl acrylate, butyl acrylate, Z-ethylhexylacrylate, methyl methacrylate, tert.-butyl methacrylate, cyclohexylmethacrylate, acrylonitrile, methacrylonitrile, acrylic acid,methacrylic acid, styrene, o-chlorostyrene and u-methyl styrene. Styreneand methyl methacrylate are the preferred monomers.

This first stage is preferably non-crosslinked, which means thatpreferably no polyethylenically unsaturated monomer is added to themonomer mixture from which the first stage is formed. However, whereverthe first stage is crosslinked, it is preferably polymerized from amonomer mixture containing 0.2 to 6.0 weight percent polyfunctionalcrosslinking monomer. The term polyfunctional crosslinking monomer iswell known and refers to a distinct art-recognized group. As used inthis specification and the claims, the term includes difunctional orbifunctional crosslinking monomers, that is monomers containing tworeactive or functional groups, as well as monomers containing more thantwo reactive or functional groups. Monomers which have this ability touniformly crosslink the first stage are those which can be incorporatedevenly in the polymerization reaction and independently of the extent ofthe completion of the reaction. In other words, their rate ofconsumption is essentially the same as that of the principal monomersuch as the alkyl acrylate. It is therefore preferred to use as thecrosslinking monomer an alkylene glycol diacrylate such as ethyleneglycol diacrylate, 1,3-butylene glycol diacrylate, l,4-butylene glycoldiacrylate, and propylene glycol diacrylate. Other crosslinking monomerssuch as the corresponding dimethacrylates to the diacrylates above, divinyl benzene, divinyl adipate or diallyl phthalate also may be used.

The term monomer mixture in this specification encompasses a solution,suspension, emulsion or mixture of components or any polymerizablecombination of monomers.

There is no restriction on the combination of monomers mentioned above,used to form the first stage except that they form a polymercharacterized by a glass transition temperature of 60 C. or less,preferably 25 C. or less. Glass transition temperatures and theirdetermination are well known to those skilled in the art as evidenced byPolymer Handbook, Brandrup et al., Interscience Publishers, Div. of J.Wiley and Sons, Inc. (1966), p. III61 to III63; High Polymers, vol. VI;Monomeric Acrylic Esters, Riddle, Reinhold Publishing Corporation(1954), pp. 58 to 64; and T. G. Fox, Bull. Am. Physics Soc., vol. 1, No.3, p. 123 (1956).

The final stage of the processing aids of this invention is a relativelyhard, substantially thermoplastic stage polymerized in the presence ofthe first stage from a monomer mixture of at least one polymerizablemonoethylenically unsaturated monomer to form a polymeric stage inintimate contact with the first stage. The final stage polymerizationforms a polymer in intimate contact with the first stage. In other wordsthe final stage is the next succeeding stage in relationship to thefirst stage and sequentially produced polymers characterized byintermediate stages, e.g. such as a stage polymerized from styrene,between the first stage and the final stage are excluded from thepresent invention.

The monomers used to form the final stage may be any of the suitablemonomers mentioned above as suitable for forming the first elastornericstage so long as this stage is characterized in that if the mixture ofmonomers were polymerized in the absence of the first stage, a productwould be formed having a glass transition temperature greater than thatof the first stage. Generally the final stage may be characterized inthat it would have a glass transition temperature greater than 25 C.,preferably greater than 60 C. Preferred monomers are methylmethacrylate, styrene or a-methylstyrene, acrylonitrile and acombination of ethyl acrylate and methyl methacrylate and a combinationof styrene and acrylonitrile.

Preferred compositions are characterized by a first noncrosslinked stagepolymerized from a monomer mixture of 1.5 to 100, or 25 to 95, weightpercent of an alkyl acrylate wherein the alkyl group contains 1 to 4carbon atoms and 0 to 98.5 or 5 to weight percent of styrene or methylmethacrylate and a final substantially thermoplastic stage polymerizedfrom a monomer mixture of 1.5 to 100 or 40 to 95 weight percent methylmethacrylate and 0 to 98.5, or 5 to 60 weight percent of a differentcopolymerizable monoethylenically unsaturated mono-mer such as styreneor ethyl acrylate. Another preferred composition is characterized by afinal rigid stage polymerized from to 70 weight percent styrene and 10to 30 weight. percent acrylonitrile.

The present invention encompasses both compatible and incompatibleprocessing aids as those terms are used in the PVC modifier art. Thepresent invention also encompasses processing aids in which one or morestages is made up of monomers in such proportions so that the refractiveindex of the resulting stage or stages is matched to the refractiveindex of the PVC resin thus resulting in a clear composition.

polymerization procedure utilizing a multi-stage or sequentialtechnique. The term monomer mixture in this specification encompasses asolution, suspension, emulsion or mixture of components or anypolymerizable combination of monomers. The monomers of the initialstage, together with polymerization initiators, soap or emulsifiers,polymerization modifiers and chain transfer agents and the like areformed into the initial polymerization mix and polymerized, e.g. byheating and mixing the emulsion, in Well known and wholly conventionalfashion, until the monomers are substantially depleted and a seedpolymer is formed. Monomers of the second, and in turn, of each, if any,additional stage are then added with appropriate other materials e.g.supplementary initiators, soap, modifiers, and the like, so that thedesired polymerizations of each stage occurs in sequence to substantialexhaustion of the monomers. In each stage subsequent to the first, theamounts of the initiator and soap, if any, are maintained at a levelsuch that polymerization occurs at or near the surface of the existingparticles, and no substantial number of new particles, or seeds, form inthe emulsion. The stages vary in hardness, from a relatively softelastomer first stage seed to the hard rigid thermoplastic final stage.Both the elastomer and the rigid thermoplastic can contain chaintransfer agents, in one or all stages, and, if desired the rigidthermoplastic stage can contain polyfunctional crosslinking monomers.However, it is a characteristic of the preferred embodiment of thepresent invention that the first soft Stage is non-crosslinked. What ismeant by the term non-crosslinked is that no crosslinking monomers arepresent in the monomer mix used to form the elastomer stage.

The molecular weight of the respective stages and of the resultingprocessing aid may vary over a wide range. It may be desirable though tocontrol the molecular weight of a particular stage of a particularprocessing aid within the broad scope of this invention so that, forexample, the first, relatively soft stage, is of a relatively lowmolecular weight, e.g. less than 450,000, or preferably 10,000 to50,000.

When molecular weight control is desired, numerous techniques are knownfor accomplishing such and there is no criticality in the presentinvention in any particular technique. However, when it is desirable tocontrol molecular weight, a preferred method is the use of a chaintransfer agent such as an alkyl mercaptan in the polymerization mix ofthe first stage. Suitable chain transfer agents in this inventioninclude the C to C and higher alkyl mercaptans particularly n-dodecylmercaptan. Other techniques for controlling molecular weight of thefirst stage include the use of peroxide, operations at high temperaturesor the use of allyl compounds.

The polymerization reactions can be initiated by either thermal or redoxtype initiator systems. Examples of thermal initiators include theorganic peroxides, such as benzoyl peroxide, substituted benzoylperoxides, acetyl peroxides, lauroyl peroxide, t-butyl hydroperoxide,di-t-butyl hydroperoxide, peresters, such as t-butyl peroxypivalate,azo-type initiators such as azo-bis-isobutyronitrile, persulfates, suchas sodium, potassium or ammonium persulfate, and peroxyphosphates suchas sodium, potassium, or ammonium peroxyphosphate. Redox initiators aregenerally a combination of a hydroperoxide, such as hydrogen peroxide,t-butyl-hydroperoxide, cumene hydroperoxide, diisopropylbenzenehydroperoxide, and the like, with a reducing agent, such as a sodium,potassium, or ammonium bisulfite, metabisulfite, or hydrosulfite, sulfurdioxide, hydrazine, ferrous salts, ascorbic acid, sodium formaldehydesulfoxylate and the like, as are well known in the art.

Examples of emulsifiers or soaps suited to polymerization processes ofthe present invention include alkali metal and ammonium salts of alkyl,aryl, alkaryl, and aralkyl sulfonates, sulfates and polyether sulfates,ethoxylated fatty acids, esters, alcohols, amines, amides, alkylphenols, complex organophosphoric acids and their alkali metal andammonium salts.

The thermoplastic vinyl halide polymers of the present invention are thepolymers and copolymers of vinyl halides, preferably chlorides, widelyutilized in the production of plastic articles. These polymers arereferred to as poly(vinyl halides) or vinyl chloride polymers (PVC) inthe present invention, and for most all uses must be modified,compounded or copolymerized with other materials to provide processableand useful compositions. For the purpose and scope of this specificationthe terms poly(vinyl halide) or vinyl chloride halide or PVC resins orlike terms will include all compositions which have vinyl chloride orother halide as the major (greater than 50%) component monomer. Thecompositions include but are not limited to: poly(vinyl chloride) [PVC],copolymers of vinyl chloride with other monomers that include vinylalkanoates such as vinyl acetate and the like, vinylidene halides suchas vinylidene chloride, alkyl esters of carboxylic acids such as acrylicacid, ethyl acrylate, Z-ethylhexyl acrylate and the like, unsaturatedhydrocarbons such as ethylene, propylene, isobutylene and the like,allyl compounds such as allyl acetate and the like; for flexibilityvinyl halide polymers are often compounded with plasticizers such asdioctyl phthalate, poly(propylene adipate) and the like, and othermodifiers such as chlorinated polyethylene;methacrylate/butadiene/styrene polymers; acrylonitrile/butadiene/styrenepolymers; ethylene/vinyl acetate polymers, and many other materials areoften included. For general applications vinyl chloride polymers withFikentscher K-values in the range of 40 to 95, preferably about 50 to75, are used. The Fikentscher K-values is determined by the formula Log[1 rel.

where C is 0.5 gm./ 100 ml. concentration of polymer in solvent,

[1 rel. is relative viscosity in cyclohexanone at 25 C.

and

K is Fikentscher value.

When copolymers of vinyl chloride are utilized in the practice of thepresent invention, it is usually preferable to utilize a polymercontaining from 0 to 15 weight percent of comonomer. The preferredcomonomers are preferably vinyl alkanoates, such as vinyl acetate, andethylene and propylene. The most preferable copolymer contains up to 10weight percent of the comonomer, with the remainder being vinylchloride. These copolymers of vinyl chloride and another monomer,mentioned above, are often softer than homopolymers of vinyl chloride.

Finally, the most preferred polymers and the polymers which are mosteffectively modified by the composite interpolymers of the presentinvention are the homopolymers of vinyl chloride and copolymers of vinylchloride and vinyl acetate, ethylene or propylene. As pointed out above,the processing aids of the present invention find particular utilitywith relatively lower molecular weight vinyl halide polymers. For thisreason,

- the vinyl halide polymer in which the processing aids find theirgreatest use is characterized by a Fikentscher K-value in the range of50 to 60.

The above copolymers vary in physical characteristics such as viscosity,and molecular weight. The copolymers generally are of slightly lowermolecular weights than PVC. Also, the viscosity values are oftenslightly lower, although generally within the above range. Thesedifferences however, are not limiting to the present invention which isdirected to modifying such polymers and not the polymers themselves. Thepolymers, however, as is obvious, must be suitable for the use desiredwhen modified, and physically must be of a type to which the presentmodifiers can be added.

Blends of the multi-stage polymer and the vinyl halide polymer can beaccomplished by any convenient technique. Entirely satisfactory blendscan be accomplished on a roll mill at convenient and customary operatingconditions, such as about 350 F. in about minutes or less time. Drymixing techniques, as with a mechanical mixer-blender device, can alsobe employed. The powder blends can, if desired, be processed incommercial extrusion equipment at conditions varying with the molecularweight of the polyvinyl halide used and the equipment employed for thatpurpose. The resulting compositions may contain 70 to 99 weight percentof the poly(vinyl halide) and about 1 to 30 weight percent of the multistage polymer processing aid. Preferably the compositions contain 1.5 toweight percent of the processing aid with 98.5 to 90 percent PVC andmost preferably comprise 2 to less than 5 percent by weight multi-stagepolymer with 98 to more than 95 percent by weight PVC resin.

Certain lubricants, stabilizers, and the like are often incorporated inthe blends. The stabilizers serve to prevent the breakdown of thepolyvinyl halide and are of several different types. Two varietiesstabilize against thermal and ultraviolet light stimulated oxidativedegradation, discoloration, and the like.

Other additives to the blends prepared in accordance with the presentinvention may include colorants, includ ing organic dyes, such asanthraquinone red, and the like, organic pigments and lakes such asphthalocyanine blue and the like, and inorganic pigments such astitanium dioxide, cadmium sulfide, and the like; fillers and particulateextenders such as carbon black, amorphous silica, asbestos, glassfibers, magnesium carbonate, and the like; plasticizers such as dioctylphthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils,and the like; and impact modifiers such as typicalmethacrylate/butadiene/styrene modifiers and others.

While only a few of such materials have been specifically recited, it isnot intended to exclude others; the recitation is exemplary only, andeach category of additives is common and well-known in the art. Theinclusions can be made at any stage of preparation in accordance withaccepted techniques well-known to those ordinarily skilled in the art,in proportions which are commonly employed. Such additional materialsare not of particular significance in the present invention.

To assist those skilled in the art in the practice of the presentinvention, the following modes of operation are set forth asillustrations, parts and percentages mean by weight unless otherwisespecifically noted. The following abbreviations are used; acrylonitrile(AN), butyl acrylate (BA), ethyl acrylate (EA), methyl methacrylate(MMA) and styrene (S); is used to divide monomers of the same stage andseparates the different stages of the sequentially produced polymers.

EXAMPLE 1 The following procedure illustrates a process for making themulti-stage acrylic composite polymers of the present invention. Thepolymer illustrated is characterized by a butyl acrylate/ styrene/ ethylacrylate/methyl methacrylate (38.4/57.6/0.4/3.6) first stage (T 18 C.)and a methyl methacrylate/styrene (54/46) second stage ('I 104 C.) wherethe ratio of the first stage to the second stage is 1/9.

Two parts of acetic acid (5% aqueous solution) and 881 parts ofdistilled water are mixed under nitrogen with stirring. The temperatureis adjusted to 40 C. and 82 parts of a monomer mixture is added. Themonomer mixture contains 5 parts acetic acid (5% aqueous solution), 6.5parts sodium lauryl sulfate, 170 parts of distilled water, partsn-dodecyl mercaptan, 192 parts n-butyl acrylate, 288 parts styrene, 2parts ethyl acrylate, 18 parts methyl methacrylate, and 5 parts cumenehydroperoxide. A solution (25 parts) of 1 part sodium sulfoxylateformaldehyde in 25 parts water is added and the nitrogen sparge isreduced. Over 1.5 hours an additional 618 parts of the above monomer mixare added. After the reaction is completed, the product is filtered andthe emulsion is evaporated in a vacuum oven for 2 to 3 days at 60 C. togive a semi-solid material [a1] acet0ne=0.13.

Distilled water, 897 parts, and 287 parts of an emulsion of thepreceding prepared polymer parts solids) are mixed under nitrogensparge. The temperature is adjusted to 44-45 C. and a solution (0.81parts) of 5 parts sodium sulfoxylate formaldehyde in 5 parts water isadded. A monomeric mixture (1076.18 parts) is then added to the reactionmixture over one hour. The monomer mixture contains parts of a 10%aqueous solution of sodium lauryl sulfate, parts of distilled water, 437parts methyl methacrylate, 373 parts styrene and 1.18 parts cumenehydroperoxide. The resulting product is cooled and filtered throughcheesecloth. An aliquot of the emulsion is evaporated in a vacuum ovenfor 2 to 3 days at 60 C. to yield a solid of [1 methyl ethyl ketone(MEK)=0.98. The balance of the emulsion is spraydried.

Sample B is similar to sample A above except the ratio of Stage I toStage II is 1/ 3. Sample C is similar to A except the Stage IIcomposition is methyl methacrylate/ ethyl acrylate=9/ 1. Samples D, Eand F are like C except the Stage I to Stage II ratios are 1/3, 1/1 and3/2 respectively.

EXAMPLE 2 The acrylic modifiers A through F, as prepared in Example 1were all dry blended into the following formulation:

90 parts medium to high molecular weight PVC 10 parts processing aid asshown 1 part tin heat stabilizer 0.5 part stearic acid The blends areall milled for 7 minutes at 350 F. and pressed at 350 F. into 100 milsheets for physical testing. Mill-processing is qualitatively rated asto rolling bank (RB), thermoplasticity (TI-I), hot strength (HS), andrelease from mill roll (Rel.), as poor (P), fair (F), good (G), andexcellent (E). Typical physical tests include Izod impact strength, ASTMD256-56A (Izod), clarity as measured by percent total white lighttransmittance (percent WL) and percent haze as measured by thedifference between the total light transmittance through the sheet lessthe parallel light transmittance divided by the total lighttransmittance, static heat stability in a 350 F. oven as measured byhours to color or hours to char, crease-whitening resistance (CWR) asrated on a qualitative numerical scale wherein 0 is no crease-whiteningand 10 is poor resistance, and other physical properties. Milled, butunpressed sheets are chopped and submitted for determination of meltviscosity [(1;) as measured in poises] and die-swell in aSieglatf-McKelvey Rheometer at 400 F. at a shear rate of 10 seconds-Dispersibility of the acrylic modifier in the PVC resin is determined ina similar composition containing a low molecular weight propylene/vinylchloride copolymer. Dispersibility is rate on a qualitative numericalscale from 0 to 10, wherein 0 is excellent and 10 is poor.

Additional details of typical formulations, processing techniques andtest procedures are provided in Rohm and Haas Company Technical BulletinTesting and Evaluation of Paraplex and Monoplex Plasticizers, No. MR-80,June 1968, printed and made available through the Resins Department ofRohm and Haas Company, Philadelphia, Pa. 19105.

Typical properties obtained with the acrylic modifiers prepared inExample 1 and the molding compositions containing these modifiers areprovided in Table 1. The results shown in this Table indicate that theimprovement in processing characteristics of PVC compositions decreasessubstantially as the proportion of soft stage in the sequentiallyproduced polymer is increased above 30 5. The composition of Claim 1wherein the first stage percent. is polymerized from a monomer mixtureof 25 to 95 TABLE 1 Dynamic heat Processing (350 F.) Clarity Rheologystability 385 F. M 5

x- Dispersi- Rolling Thermo- Hot Percent Percent Percent Min. to Min. toIzod Sample bility bank plasticity strength Release WL haze Poises swellstick char impact Stg.I Stg. II

5 G- G+ E- G 86.5 5.6 7,293 9 s 33 0.46 0.19 7.5 1 G- E- G- G 57.3 4.95,834. 7 59 44 1. 04 0.19 11.0 7 G- E- E- G 84.5 7.1 9,110 31 17 35 0.540.19 9.0 2 G- E- G 84.7 5.5 7, 475 19 2a 40 0.51 0.19 5.9 0-1 F G- F+ G0.19 10.0 0-1 F F+ G o. 19 15.0

EXAMPLE 3 weight percent of an alkyl acrylate which is ethyl acrylate orbutyl acrylate and correspondingly 5 to 75 weight The followingcompositions shown in Table 2 are prepercent of at least one differentcopolymerizable m'onopared according to the procedure of Example 1 andare ethylenically unsaturated monomer. I incorporated into PVC accordingto Example 2. The 6. The composition of Glam 5 wherein the differentTable 2 presents mill processing, dispersion and other copolymerizablemonoethylenically unsaturated monocharacteristics of the resultingcompositions. 20 mer of the first stage is styrene or methylmethacrylate.

TABLE 2 Clarity Mill processing, 350 F.

Percent Dispersi- Flux time Rolling Hot Thermowhite light PercentComposition bility (min.) bank strength plasticity Release transmissionhaze First stage*/IMMA/EA 10//81/9 7 G- E- E G 84. 5 7. 1 Firststagel/MMA/EA //67.5/7.5 2 G- G E- G 84.7 5.5 EA/lMMA/S 10/48.6l41.4 4-5G G E E- 83.5 5.9 EAl/MMA/S 25//40.5/34.5 2-3 G G F G 81.4 7.9

*First stage is BA/S/MMA/EA; 23/34.6/2.2/0.2 parts by weight. What isclaimed is: 7. The composition of Claim 1 wherein the final stage L Acomposition f improved processability is polymerized from a monomermixture of 1.5 to 100 prising about 70 to 99' weight percent of apoly(viny1 Weight percent methyl methacrylate and O to 98.5 Weighthalide) and about 1.0 to weight percent of a two- Percent Styrene 9 3 yfi stage sequentially produced polymer characterized by 1 Thecfmlposltlon of Clalm 5 W1 1efe1n the final Stage to 25 weight percentof (A) a first relatively soft stage 15 polymerlzed from a omer mixtureof 1.5 to 100 polymerized f a monomer mixture f L5 to 100 weight percentmethyl methacrylate and 0 to 98.5 weight weight percent of an alkylacrylate wherein said alkyl Pewter!t Styrene E y yla group has 1 to 18carbon atoms, correspondingly 0 to 40 The cfmlposltlon of Clalm 1 wheremhe final stag 98.5 Weight percent of at least one different copolym- 1sPolymenzed from mOHOmef l tllle 0f 40 to 95 erizable monoethylenicallyunsaturated monomer, and welsht Percent methyl yl e and 5 to 60 0 to 10weight percent of a copolymerizable polyfunc- Welght P t tyrene or ethylacrylate.

tional crosslinking monomer, said first stage further 90111190513011 ofClalm 5 e in the final characterized by a glass transition temperatureof 60 C. Staga Polymenzed from a monomer mixture of 40 to or less; and99 to 75 weight percent of (B) a final, rela- 95 We1ght Percent hylmethacrylate and 5 to 60 tively hard, substantially thermoplastic stagepolymer- Welghtpercent W p y fy ized in the presence of said first stagefrom a monomer corflposltlon 9 Clalm ln the p013- mixture of at leastone polymerizable monoethylenically W hahde) 15 a P Y Y chlol'lde)terlled by unsaturated monomer to form a polymer in intimate aFlkemscher 111 the f 0f 5 60- contact with the first stage, stage (B)further characcomposltlon of clalm 11 Whereln Q P terized in that, ifsaid monomer of monomers were (vmyl hahde) a homolfolymer V1I1Y1chlorlde Or a polymerized in the absence of said first Stage, a Polymercopolymer of vinyl chlorlde and vlnylacetate, ethylene would be formedhaving a glass transition temperature or Propylene' greater than that ofthe first stage and of 25 C. or References Clted greater. UNITED STATESPATENTS 2. The composition of Claim 1 wherein the first stage icharacterized by a glass transition temperature of 3,552,235 2/1971 R260-885 25 C. or less and the final stage would have a glass 3 3 at O 011 61 e a transition temperature of C. or greater. 3,655,825 4/1972Souder et all u 260 876R 3. The composition of Claim 1 wherein thesequen- 3 678133 7/1972 Ryan 260 876R tially produced polymer is a twostage polymer characterized by 5 to 25 Weight percent of the first stageand MURRAY TILLMAN, p i Examiner 95 to weight percent of the finalstage. 65 RICHARD B TURER Assistant Examiner 4. The composition of Claim1 wherein the sequentially dprtpdusced gcslymerhis a two stzjifgehpoymercharacci c1 terize y to Weig t percent 0 t e st stage an I 95 to weightpercent of the final stage. 260-23 XA, 23.5 R, 31.8 M, 33.6 UA, 45.75 K,41 A,

41 B, 41 C, 41 AG, 881,884, 885, 886

